1. Field of the Invention
The present invention relates to a sheet processing apparatus that binds a sheet bundle including a plurality of sheets, and an image forming apparatus provided with the sheet processing apparatus.
2. Description of the Related Art
In recent years, there has been increasing a demand for a process of binding sheets, having an image recorded thereon by an image forming apparatus such as a copying machine or a printer, into a booklet form as a conference material or a distributed material. As a sheet processing apparatus that meets the demand described above, there has conventionally widely been used a staple apparatus that binds a sheet bundle, including plural sheets, with a binding member such as a metal needle.
On the other hand, recycling a used sheet has attracted attention in recent years from the viewpoint of environmental protection. In order to recycle the sheet, the sheet bundle bound with the metal needle has to be collected in such a manner that the metal needle is removed from the sheet, and the sheet and the metal needle are separated, which is a troublesome task. The sheet can be reused, but the metal needle is dumped as a waste after it is used, which entails wasteful spending and a waste of resources.
In view of this, there has been proposed a sheet binding apparatus that does not use a metal needle in order to reduce labor upon recycling, reduce the waste of resources and recycle a sheet (Japanese Patent Application Laid-Open No. 6-72060). However, in the above-mentioned sheet binding apparatus, binding force cannot be adjusted because a binding area cannot be changed. There has also been proposed a sheet binding apparatus that includes plural blades as a half-blanking portion not using a metal needle, wherein binding force can be adjusted by changing the half-blanking direction of the plural blades (Japanese Patent Application Laid-Open No. 2009-51661).
However, when the sheet bundle is bound by a half-blanking without using a metal needle such as the above-mentioned half-blanking portion, a binding portion or a binding area has to increase in order to further strengthen the binding of the sheet bundle.
In this case, it is considered that plural types of cutters, each having a different shape and different binding area, are prepared beforehand, and the cutter according to the purpose is selected from the plural types of cutters so as to perform a binding process.
However, the configuration of selectively using the plural types of cutters entails problems that it takes time to change the cutter and the productivity is decreased.
An object of the present invention is to be capable of setting a binding area, where an asperity is formed on a sheet bundle, to be an optional size, while preventing the deterioration in productivity.